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3dcf60bc | 1 | // SPDX-License-Identifier: GPL-2.0 |
d7067512 JB |
2 | /* |
3 | * Block rq-qos base io controller | |
4 | * | |
5 | * This works similar to wbt with a few exceptions | |
6 | * | |
7 | * - It's bio based, so the latency covers the whole block layer in addition to | |
8 | * the actual io. | |
9 | * - We will throttle all IO that comes in here if we need to. | |
10 | * - We use the mean latency over the 100ms window. This is because writes can | |
11 | * be particularly fast, which could give us a false sense of the impact of | |
12 | * other workloads on our protected workload. | |
a284390b JB |
13 | * - By default there's no throttling, we set the queue_depth to UINT_MAX so |
14 | * that we can have as many outstanding bio's as we're allowed to. Only at | |
d7067512 JB |
15 | * throttle time do we pay attention to the actual queue depth. |
16 | * | |
17 | * The hierarchy works like the cpu controller does, we track the latency at | |
18 | * every configured node, and each configured node has it's own independent | |
19 | * queue depth. This means that we only care about our latency targets at the | |
20 | * peer level. Some group at the bottom of the hierarchy isn't going to affect | |
21 | * a group at the end of some other path if we're only configred at leaf level. | |
22 | * | |
23 | * Consider the following | |
24 | * | |
25 | * root blkg | |
26 | * / \ | |
27 | * fast (target=5ms) slow (target=10ms) | |
28 | * / \ / \ | |
29 | * a b normal(15ms) unloved | |
30 | * | |
31 | * "a" and "b" have no target, but their combined io under "fast" cannot exceed | |
32 | * an average latency of 5ms. If it does then we will throttle the "slow" | |
33 | * group. In the case of "normal", if it exceeds its 15ms target, we will | |
34 | * throttle "unloved", but nobody else. | |
35 | * | |
36 | * In this example "fast", "slow", and "normal" will be the only groups actually | |
37 | * accounting their io latencies. We have to walk up the heirarchy to the root | |
38 | * on every submit and complete so we can do the appropriate stat recording and | |
39 | * adjust the queue depth of ourselves if needed. | |
40 | * | |
41 | * There are 2 ways we throttle IO. | |
42 | * | |
43 | * 1) Queue depth throttling. As we throttle down we will adjust the maximum | |
44 | * number of IO's we're allowed to have in flight. This starts at (u64)-1 down | |
45 | * to 1. If the group is only ever submitting IO for itself then this is the | |
46 | * only way we throttle. | |
47 | * | |
48 | * 2) Induced delay throttling. This is for the case that a group is generating | |
49 | * IO that has to be issued by the root cg to avoid priority inversion. So think | |
50 | * REQ_META or REQ_SWAP. If we are already at qd == 1 and we're getting a lot | |
51 | * of work done for us on behalf of the root cg and are being asked to scale | |
52 | * down more then we induce a latency at userspace return. We accumulate the | |
53 | * total amount of time we need to be punished by doing | |
54 | * | |
55 | * total_time += min_lat_nsec - actual_io_completion | |
56 | * | |
57 | * and then at throttle time will do | |
58 | * | |
59 | * throttle_time = min(total_time, NSEC_PER_SEC) | |
60 | * | |
61 | * This induced delay will throttle back the activity that is generating the | |
62 | * root cg issued io's, wethere that's some metadata intensive operation or the | |
63 | * group is using so much memory that it is pushing us into swap. | |
64 | * | |
65 | * Copyright (C) 2018 Josef Bacik | |
66 | */ | |
67 | #include <linux/kernel.h> | |
68 | #include <linux/blk_types.h> | |
69 | #include <linux/backing-dev.h> | |
70 | #include <linux/module.h> | |
71 | #include <linux/timer.h> | |
72 | #include <linux/memcontrol.h> | |
c480bcf9 | 73 | #include <linux/sched/loadavg.h> |
d7067512 JB |
74 | #include <linux/sched/signal.h> |
75 | #include <trace/events/block.h> | |
8c772a9b | 76 | #include <linux/blk-mq.h> |
e41d12f5 | 77 | #include <linux/blk-cgroup.h> |
d7067512 JB |
78 | #include "blk-rq-qos.h" |
79 | #include "blk-stat.h" | |
373e915c | 80 | #include "blk.h" |
d7067512 JB |
81 | |
82 | #define DEFAULT_SCALE_COOKIE 1000000U | |
83 | ||
84 | static struct blkcg_policy blkcg_policy_iolatency; | |
85 | struct iolatency_grp; | |
86 | ||
87 | struct blk_iolatency { | |
88 | struct rq_qos rqos; | |
89 | struct timer_list timer; | |
90 | atomic_t enabled; | |
91 | }; | |
92 | ||
93 | static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) | |
94 | { | |
95 | return container_of(rqos, struct blk_iolatency, rqos); | |
96 | } | |
97 | ||
98 | static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat) | |
99 | { | |
100 | return atomic_read(&blkiolat->enabled) > 0; | |
101 | } | |
102 | ||
103 | struct child_latency_info { | |
104 | spinlock_t lock; | |
105 | ||
106 | /* Last time we adjusted the scale of everybody. */ | |
107 | u64 last_scale_event; | |
108 | ||
109 | /* The latency that we missed. */ | |
110 | u64 scale_lat; | |
111 | ||
112 | /* Total io's from all of our children for the last summation. */ | |
113 | u64 nr_samples; | |
114 | ||
115 | /* The guy who actually changed the latency numbers. */ | |
116 | struct iolatency_grp *scale_grp; | |
117 | ||
118 | /* Cookie to tell if we need to scale up or down. */ | |
119 | atomic_t scale_cookie; | |
120 | }; | |
121 | ||
1fa2840e JB |
122 | struct percentile_stats { |
123 | u64 total; | |
124 | u64 missed; | |
125 | }; | |
126 | ||
127 | struct latency_stat { | |
128 | union { | |
129 | struct percentile_stats ps; | |
130 | struct blk_rq_stat rqs; | |
131 | }; | |
132 | }; | |
133 | ||
d7067512 JB |
134 | struct iolatency_grp { |
135 | struct blkg_policy_data pd; | |
1fa2840e | 136 | struct latency_stat __percpu *stats; |
451bb7c3 | 137 | struct latency_stat cur_stat; |
d7067512 JB |
138 | struct blk_iolatency *blkiolat; |
139 | struct rq_depth rq_depth; | |
140 | struct rq_wait rq_wait; | |
141 | atomic64_t window_start; | |
142 | atomic_t scale_cookie; | |
143 | u64 min_lat_nsec; | |
144 | u64 cur_win_nsec; | |
145 | ||
146 | /* total running average of our io latency. */ | |
c480bcf9 | 147 | u64 lat_avg; |
d7067512 JB |
148 | |
149 | /* Our current number of IO's for the last summation. */ | |
150 | u64 nr_samples; | |
151 | ||
1fa2840e | 152 | bool ssd; |
d7067512 JB |
153 | struct child_latency_info child_lat; |
154 | }; | |
155 | ||
c480bcf9 DZF |
156 | #define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC) |
157 | #define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC | |
158 | /* | |
159 | * These are the constants used to fake the fixed-point moving average | |
8508cf3f | 160 | * calculation just like load average. The call to calc_load() folds |
c480bcf9 DZF |
161 | * (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling |
162 | * window size is bucketed to try to approximately calculate average | |
163 | * latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows | |
164 | * elapse immediately. Note, windows only elapse with IO activity. Idle | |
165 | * periods extend the most recent window. | |
166 | */ | |
167 | #define BLKIOLATENCY_NR_EXP_FACTORS 5 | |
168 | #define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \ | |
169 | (BLKIOLATENCY_NR_EXP_FACTORS - 1)) | |
170 | static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = { | |
171 | 2045, // exp(1/600) - 600 samples | |
172 | 2039, // exp(1/240) - 240 samples | |
173 | 2031, // exp(1/120) - 120 samples | |
174 | 2023, // exp(1/80) - 80 samples | |
175 | 2014, // exp(1/60) - 60 samples | |
176 | }; | |
177 | ||
d7067512 JB |
178 | static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd) |
179 | { | |
180 | return pd ? container_of(pd, struct iolatency_grp, pd) : NULL; | |
181 | } | |
182 | ||
183 | static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg) | |
184 | { | |
185 | return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency)); | |
186 | } | |
187 | ||
188 | static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat) | |
189 | { | |
190 | return pd_to_blkg(&iolat->pd); | |
191 | } | |
192 | ||
1fa2840e JB |
193 | static inline void latency_stat_init(struct iolatency_grp *iolat, |
194 | struct latency_stat *stat) | |
195 | { | |
196 | if (iolat->ssd) { | |
197 | stat->ps.total = 0; | |
198 | stat->ps.missed = 0; | |
199 | } else | |
200 | blk_rq_stat_init(&stat->rqs); | |
201 | } | |
202 | ||
203 | static inline void latency_stat_sum(struct iolatency_grp *iolat, | |
204 | struct latency_stat *sum, | |
205 | struct latency_stat *stat) | |
206 | { | |
207 | if (iolat->ssd) { | |
208 | sum->ps.total += stat->ps.total; | |
209 | sum->ps.missed += stat->ps.missed; | |
210 | } else | |
211 | blk_rq_stat_sum(&sum->rqs, &stat->rqs); | |
212 | } | |
213 | ||
214 | static inline void latency_stat_record_time(struct iolatency_grp *iolat, | |
215 | u64 req_time) | |
216 | { | |
217 | struct latency_stat *stat = get_cpu_ptr(iolat->stats); | |
218 | if (iolat->ssd) { | |
219 | if (req_time >= iolat->min_lat_nsec) | |
220 | stat->ps.missed++; | |
221 | stat->ps.total++; | |
222 | } else | |
223 | blk_rq_stat_add(&stat->rqs, req_time); | |
224 | put_cpu_ptr(stat); | |
225 | } | |
226 | ||
227 | static inline bool latency_sum_ok(struct iolatency_grp *iolat, | |
228 | struct latency_stat *stat) | |
229 | { | |
230 | if (iolat->ssd) { | |
231 | u64 thresh = div64_u64(stat->ps.total, 10); | |
232 | thresh = max(thresh, 1ULL); | |
233 | return stat->ps.missed < thresh; | |
234 | } | |
235 | return stat->rqs.mean <= iolat->min_lat_nsec; | |
236 | } | |
237 | ||
238 | static inline u64 latency_stat_samples(struct iolatency_grp *iolat, | |
239 | struct latency_stat *stat) | |
240 | { | |
241 | if (iolat->ssd) | |
242 | return stat->ps.total; | |
243 | return stat->rqs.nr_samples; | |
244 | } | |
245 | ||
246 | static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat, | |
247 | struct latency_stat *stat) | |
248 | { | |
249 | int exp_idx; | |
250 | ||
251 | if (iolat->ssd) | |
252 | return; | |
253 | ||
254 | /* | |
8508cf3f | 255 | * calc_load() takes in a number stored in fixed point representation. |
1fa2840e JB |
256 | * Because we are using this for IO time in ns, the values stored |
257 | * are significantly larger than the FIXED_1 denominator (2048). | |
258 | * Therefore, rounding errors in the calculation are negligible and | |
259 | * can be ignored. | |
260 | */ | |
261 | exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1, | |
262 | div64_u64(iolat->cur_win_nsec, | |
263 | BLKIOLATENCY_EXP_BUCKET_SIZE)); | |
8508cf3f JW |
264 | iolat->lat_avg = calc_load(iolat->lat_avg, |
265 | iolatency_exp_factors[exp_idx], | |
266 | stat->rqs.mean); | |
1fa2840e JB |
267 | } |
268 | ||
d3fcdff1 | 269 | static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data) |
d7067512 | 270 | { |
d3fcdff1 JB |
271 | atomic_dec(&rqw->inflight); |
272 | wake_up(&rqw->wait); | |
273 | } | |
d7067512 | 274 | |
d3fcdff1 JB |
275 | static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data) |
276 | { | |
277 | struct iolatency_grp *iolat = private_data; | |
d7067512 JB |
278 | return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth); |
279 | } | |
280 | ||
281 | static void __blkcg_iolatency_throttle(struct rq_qos *rqos, | |
282 | struct iolatency_grp *iolat, | |
d5337560 | 283 | bool issue_as_root, |
d7067512 | 284 | bool use_memdelay) |
d7067512 JB |
285 | { |
286 | struct rq_wait *rqw = &iolat->rq_wait; | |
287 | unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay); | |
d7067512 JB |
288 | |
289 | if (use_delay) | |
290 | blkcg_schedule_throttle(rqos->q, use_memdelay); | |
291 | ||
292 | /* | |
293 | * To avoid priority inversions we want to just take a slot if we are | |
294 | * issuing as root. If we're being killed off there's no point in | |
295 | * delaying things, we may have been killed by OOM so throttling may | |
296 | * make recovery take even longer, so just let the IO's through so the | |
297 | * task can go away. | |
298 | */ | |
299 | if (issue_as_root || fatal_signal_pending(current)) { | |
300 | atomic_inc(&rqw->inflight); | |
301 | return; | |
302 | } | |
303 | ||
d3fcdff1 | 304 | rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb); |
d7067512 JB |
305 | } |
306 | ||
307 | #define SCALE_DOWN_FACTOR 2 | |
308 | #define SCALE_UP_FACTOR 4 | |
309 | ||
310 | static inline unsigned long scale_amount(unsigned long qd, bool up) | |
311 | { | |
312 | return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL); | |
313 | } | |
314 | ||
315 | /* | |
316 | * We scale the qd down faster than we scale up, so we need to use this helper | |
317 | * to adjust the scale_cookie accordingly so we don't prematurely get | |
318 | * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much. | |
319 | * | |
320 | * Each group has their own local copy of the last scale cookie they saw, so if | |
321 | * the global scale cookie goes up or down they know which way they need to go | |
322 | * based on their last knowledge of it. | |
323 | */ | |
324 | static void scale_cookie_change(struct blk_iolatency *blkiolat, | |
325 | struct child_latency_info *lat_info, | |
326 | bool up) | |
327 | { | |
ff4cee08 | 328 | unsigned long qd = blkiolat->rqos.q->nr_requests; |
d7067512 JB |
329 | unsigned long scale = scale_amount(qd, up); |
330 | unsigned long old = atomic_read(&lat_info->scale_cookie); | |
331 | unsigned long max_scale = qd << 1; | |
332 | unsigned long diff = 0; | |
333 | ||
334 | if (old < DEFAULT_SCALE_COOKIE) | |
335 | diff = DEFAULT_SCALE_COOKIE - old; | |
336 | ||
337 | if (up) { | |
338 | if (scale + old > DEFAULT_SCALE_COOKIE) | |
339 | atomic_set(&lat_info->scale_cookie, | |
340 | DEFAULT_SCALE_COOKIE); | |
341 | else if (diff > qd) | |
342 | atomic_inc(&lat_info->scale_cookie); | |
343 | else | |
344 | atomic_add(scale, &lat_info->scale_cookie); | |
345 | } else { | |
346 | /* | |
347 | * We don't want to dig a hole so deep that it takes us hours to | |
348 | * dig out of it. Just enough that we don't throttle/unthrottle | |
349 | * with jagged workloads but can still unthrottle once pressure | |
350 | * has sufficiently dissipated. | |
351 | */ | |
352 | if (diff > qd) { | |
353 | if (diff < max_scale) | |
354 | atomic_dec(&lat_info->scale_cookie); | |
355 | } else { | |
356 | atomic_sub(scale, &lat_info->scale_cookie); | |
357 | } | |
358 | } | |
359 | } | |
360 | ||
361 | /* | |
362 | * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the | |
363 | * queue depth at a time so we don't get wild swings and hopefully dial in to | |
364 | * fairer distribution of the overall queue depth. | |
365 | */ | |
366 | static void scale_change(struct iolatency_grp *iolat, bool up) | |
367 | { | |
ff4cee08 | 368 | unsigned long qd = iolat->blkiolat->rqos.q->nr_requests; |
d7067512 JB |
369 | unsigned long scale = scale_amount(qd, up); |
370 | unsigned long old = iolat->rq_depth.max_depth; | |
d7067512 JB |
371 | |
372 | if (old > qd) | |
373 | old = qd; | |
374 | ||
375 | if (up) { | |
376 | if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat))) | |
377 | return; | |
378 | ||
379 | if (old < qd) { | |
d7067512 JB |
380 | old += scale; |
381 | old = min(old, qd); | |
382 | iolat->rq_depth.max_depth = old; | |
383 | wake_up_all(&iolat->rq_wait.wait); | |
384 | } | |
9f60511a | 385 | } else { |
d7067512 | 386 | old >>= 1; |
d7067512 JB |
387 | iolat->rq_depth.max_depth = max(old, 1UL); |
388 | } | |
389 | } | |
390 | ||
391 | /* Check our parent and see if the scale cookie has changed. */ | |
392 | static void check_scale_change(struct iolatency_grp *iolat) | |
393 | { | |
394 | struct iolatency_grp *parent; | |
395 | struct child_latency_info *lat_info; | |
396 | unsigned int cur_cookie; | |
397 | unsigned int our_cookie = atomic_read(&iolat->scale_cookie); | |
398 | u64 scale_lat; | |
399 | unsigned int old; | |
400 | int direction = 0; | |
401 | ||
402 | if (lat_to_blkg(iolat)->parent == NULL) | |
403 | return; | |
404 | ||
405 | parent = blkg_to_lat(lat_to_blkg(iolat)->parent); | |
406 | if (!parent) | |
407 | return; | |
408 | ||
409 | lat_info = &parent->child_lat; | |
410 | cur_cookie = atomic_read(&lat_info->scale_cookie); | |
411 | scale_lat = READ_ONCE(lat_info->scale_lat); | |
412 | ||
413 | if (cur_cookie < our_cookie) | |
414 | direction = -1; | |
415 | else if (cur_cookie > our_cookie) | |
416 | direction = 1; | |
417 | else | |
418 | return; | |
419 | ||
420 | old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie); | |
421 | ||
422 | /* Somebody beat us to the punch, just bail. */ | |
423 | if (old != our_cookie) | |
424 | return; | |
425 | ||
426 | if (direction < 0 && iolat->min_lat_nsec) { | |
427 | u64 samples_thresh; | |
428 | ||
429 | if (!scale_lat || iolat->min_lat_nsec <= scale_lat) | |
430 | return; | |
431 | ||
432 | /* | |
433 | * Sometimes high priority groups are their own worst enemy, so | |
434 | * instead of taking it out on some poor other group that did 5% | |
435 | * or less of the IO's for the last summation just skip this | |
436 | * scale down event. | |
437 | */ | |
438 | samples_thresh = lat_info->nr_samples * 5; | |
22ed8a93 | 439 | samples_thresh = max(1ULL, div64_u64(samples_thresh, 100)); |
d7067512 JB |
440 | if (iolat->nr_samples <= samples_thresh) |
441 | return; | |
442 | } | |
443 | ||
444 | /* We're as low as we can go. */ | |
445 | if (iolat->rq_depth.max_depth == 1 && direction < 0) { | |
446 | blkcg_use_delay(lat_to_blkg(iolat)); | |
447 | return; | |
448 | } | |
449 | ||
450 | /* We're back to the default cookie, unthrottle all the things. */ | |
451 | if (cur_cookie == DEFAULT_SCALE_COOKIE) { | |
452 | blkcg_clear_delay(lat_to_blkg(iolat)); | |
a284390b | 453 | iolat->rq_depth.max_depth = UINT_MAX; |
d7067512 JB |
454 | wake_up_all(&iolat->rq_wait.wait); |
455 | return; | |
456 | } | |
457 | ||
458 | scale_change(iolat, direction > 0); | |
459 | } | |
460 | ||
d5337560 | 461 | static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio) |
d7067512 JB |
462 | { |
463 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
5cdf2e3f | 464 | struct blkcg_gq *blkg = bio->bi_blkg; |
d7067512 JB |
465 | bool issue_as_root = bio_issue_as_root_blkg(bio); |
466 | ||
467 | if (!blk_iolatency_enabled(blkiolat)) | |
468 | return; | |
469 | ||
d7067512 JB |
470 | while (blkg && blkg->parent) { |
471 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
472 | if (!iolat) { | |
473 | blkg = blkg->parent; | |
474 | continue; | |
475 | } | |
476 | ||
477 | check_scale_change(iolat); | |
d5337560 | 478 | __blkcg_iolatency_throttle(rqos, iolat, issue_as_root, |
d7067512 JB |
479 | (bio->bi_opf & REQ_SWAP) == REQ_SWAP); |
480 | blkg = blkg->parent; | |
481 | } | |
482 | if (!timer_pending(&blkiolat->timer)) | |
483 | mod_timer(&blkiolat->timer, jiffies + HZ); | |
484 | } | |
485 | ||
486 | static void iolatency_record_time(struct iolatency_grp *iolat, | |
487 | struct bio_issue *issue, u64 now, | |
488 | bool issue_as_root) | |
489 | { | |
d7067512 JB |
490 | u64 start = bio_issue_time(issue); |
491 | u64 req_time; | |
492 | ||
71e9690b JB |
493 | /* |
494 | * Have to do this so we are truncated to the correct time that our | |
495 | * issue is truncated to. | |
496 | */ | |
497 | now = __bio_issue_time(now); | |
498 | ||
d7067512 JB |
499 | if (now <= start) |
500 | return; | |
501 | ||
502 | req_time = now - start; | |
503 | ||
504 | /* | |
505 | * We don't want to count issue_as_root bio's in the cgroups latency | |
506 | * statistics as it could skew the numbers downwards. | |
507 | */ | |
a284390b | 508 | if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) { |
d7067512 JB |
509 | u64 sub = iolat->min_lat_nsec; |
510 | if (req_time < sub) | |
511 | blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time); | |
512 | return; | |
513 | } | |
514 | ||
1fa2840e | 515 | latency_stat_record_time(iolat, req_time); |
d7067512 JB |
516 | } |
517 | ||
518 | #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC) | |
519 | #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5 | |
520 | ||
521 | static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) | |
522 | { | |
523 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
524 | struct iolatency_grp *parent; | |
525 | struct child_latency_info *lat_info; | |
1fa2840e | 526 | struct latency_stat stat; |
d7067512 | 527 | unsigned long flags; |
1fa2840e | 528 | int cpu; |
d7067512 | 529 | |
1fa2840e | 530 | latency_stat_init(iolat, &stat); |
d7067512 JB |
531 | preempt_disable(); |
532 | for_each_online_cpu(cpu) { | |
1fa2840e | 533 | struct latency_stat *s; |
d7067512 | 534 | s = per_cpu_ptr(iolat->stats, cpu); |
1fa2840e JB |
535 | latency_stat_sum(iolat, &stat, s); |
536 | latency_stat_init(iolat, s); | |
d7067512 JB |
537 | } |
538 | preempt_enable(); | |
539 | ||
d7067512 JB |
540 | parent = blkg_to_lat(blkg->parent); |
541 | if (!parent) | |
542 | return; | |
543 | ||
544 | lat_info = &parent->child_lat; | |
545 | ||
1fa2840e | 546 | iolat_update_total_lat_avg(iolat, &stat); |
d7067512 JB |
547 | |
548 | /* Everything is ok and we don't need to adjust the scale. */ | |
1fa2840e | 549 | if (latency_sum_ok(iolat, &stat) && |
d7067512 JB |
550 | atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE) |
551 | return; | |
552 | ||
553 | /* Somebody beat us to the punch, just bail. */ | |
554 | spin_lock_irqsave(&lat_info->lock, flags); | |
451bb7c3 JB |
555 | |
556 | latency_stat_sum(iolat, &iolat->cur_stat, &stat); | |
d7067512 | 557 | lat_info->nr_samples -= iolat->nr_samples; |
451bb7c3 JB |
558 | lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat); |
559 | iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat); | |
d7067512 JB |
560 | |
561 | if ((lat_info->last_scale_event >= now || | |
451bb7c3 | 562 | now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME)) |
d7067512 JB |
563 | goto out; |
564 | ||
451bb7c3 JB |
565 | if (latency_sum_ok(iolat, &iolat->cur_stat) && |
566 | latency_sum_ok(iolat, &stat)) { | |
567 | if (latency_stat_samples(iolat, &iolat->cur_stat) < | |
1fa2840e JB |
568 | BLKIOLATENCY_MIN_GOOD_SAMPLES) |
569 | goto out; | |
d7067512 JB |
570 | if (lat_info->scale_grp == iolat) { |
571 | lat_info->last_scale_event = now; | |
572 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
573 | } | |
451bb7c3 JB |
574 | } else if (lat_info->scale_lat == 0 || |
575 | lat_info->scale_lat >= iolat->min_lat_nsec) { | |
d7067512 JB |
576 | lat_info->last_scale_event = now; |
577 | if (!lat_info->scale_grp || | |
578 | lat_info->scale_lat > iolat->min_lat_nsec) { | |
579 | WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec); | |
580 | lat_info->scale_grp = iolat; | |
581 | } | |
582 | scale_cookie_change(iolat->blkiolat, lat_info, false); | |
583 | } | |
451bb7c3 | 584 | latency_stat_init(iolat, &iolat->cur_stat); |
d7067512 JB |
585 | out: |
586 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
587 | } | |
588 | ||
589 | static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio) | |
590 | { | |
591 | struct blkcg_gq *blkg; | |
592 | struct rq_wait *rqw; | |
593 | struct iolatency_grp *iolat; | |
594 | u64 window_start; | |
6e2fa4dd | 595 | u64 now; |
d7067512 JB |
596 | bool issue_as_root = bio_issue_as_root_blkg(bio); |
597 | bool enabled = false; | |
391f552a | 598 | int inflight = 0; |
d7067512 JB |
599 | |
600 | blkg = bio->bi_blkg; | |
13369816 | 601 | if (!blkg || !bio_flagged(bio, BIO_TRACKED)) |
d7067512 JB |
602 | return; |
603 | ||
604 | iolat = blkg_to_lat(bio->bi_blkg); | |
605 | if (!iolat) | |
606 | return; | |
607 | ||
608 | enabled = blk_iolatency_enabled(iolat->blkiolat); | |
8c772a9b LB |
609 | if (!enabled) |
610 | return; | |
611 | ||
6e2fa4dd | 612 | now = ktime_to_ns(ktime_get()); |
d7067512 JB |
613 | while (blkg && blkg->parent) { |
614 | iolat = blkg_to_lat(blkg); | |
615 | if (!iolat) { | |
616 | blkg = blkg->parent; | |
617 | continue; | |
618 | } | |
619 | rqw = &iolat->rq_wait; | |
620 | ||
391f552a LB |
621 | inflight = atomic_dec_return(&rqw->inflight); |
622 | WARN_ON_ONCE(inflight < 0); | |
c9b3007f DZ |
623 | /* |
624 | * If bi_status is BLK_STS_AGAIN, the bio wasn't actually | |
625 | * submitted, so do not account for it. | |
626 | */ | |
627 | if (iolat->min_lat_nsec && bio->bi_status != BLK_STS_AGAIN) { | |
628 | iolatency_record_time(iolat, &bio->bi_issue, now, | |
629 | issue_as_root); | |
630 | window_start = atomic64_read(&iolat->window_start); | |
631 | if (now > window_start && | |
632 | (now - window_start) >= iolat->cur_win_nsec) { | |
633 | if (atomic64_cmpxchg(&iolat->window_start, | |
634 | window_start, now) == window_start) | |
635 | iolatency_check_latencies(iolat, now); | |
636 | } | |
d7067512 | 637 | } |
d7067512 | 638 | wake_up(&rqw->wait); |
d7067512 JB |
639 | blkg = blkg->parent; |
640 | } | |
641 | } | |
642 | ||
643 | static void blkcg_iolatency_exit(struct rq_qos *rqos) | |
644 | { | |
645 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
646 | ||
647 | del_timer_sync(&blkiolat->timer); | |
648 | blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency); | |
649 | kfree(blkiolat); | |
650 | } | |
651 | ||
652 | static struct rq_qos_ops blkcg_iolatency_ops = { | |
653 | .throttle = blkcg_iolatency_throttle, | |
d7067512 JB |
654 | .done_bio = blkcg_iolatency_done_bio, |
655 | .exit = blkcg_iolatency_exit, | |
656 | }; | |
657 | ||
658 | static void blkiolatency_timer_fn(struct timer_list *t) | |
659 | { | |
660 | struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer); | |
661 | struct blkcg_gq *blkg; | |
662 | struct cgroup_subsys_state *pos_css; | |
663 | u64 now = ktime_to_ns(ktime_get()); | |
664 | ||
665 | rcu_read_lock(); | |
666 | blkg_for_each_descendant_pre(blkg, pos_css, | |
667 | blkiolat->rqos.q->root_blkg) { | |
668 | struct iolatency_grp *iolat; | |
669 | struct child_latency_info *lat_info; | |
670 | unsigned long flags; | |
671 | u64 cookie; | |
672 | ||
673 | /* | |
674 | * We could be exiting, don't access the pd unless we have a | |
675 | * ref on the blkg. | |
676 | */ | |
7754f669 | 677 | if (!blkg_tryget(blkg)) |
d7067512 JB |
678 | continue; |
679 | ||
680 | iolat = blkg_to_lat(blkg); | |
681 | if (!iolat) | |
52a1199c | 682 | goto next; |
d7067512 JB |
683 | |
684 | lat_info = &iolat->child_lat; | |
685 | cookie = atomic_read(&lat_info->scale_cookie); | |
686 | ||
687 | if (cookie >= DEFAULT_SCALE_COOKIE) | |
688 | goto next; | |
689 | ||
690 | spin_lock_irqsave(&lat_info->lock, flags); | |
691 | if (lat_info->last_scale_event >= now) | |
692 | goto next_lock; | |
693 | ||
694 | /* | |
695 | * We scaled down but don't have a scale_grp, scale up and carry | |
696 | * on. | |
697 | */ | |
698 | if (lat_info->scale_grp == NULL) { | |
699 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
700 | goto next_lock; | |
701 | } | |
702 | ||
703 | /* | |
704 | * It's been 5 seconds since our last scale event, clear the | |
705 | * scale grp in case the group that needed the scale down isn't | |
706 | * doing any IO currently. | |
707 | */ | |
708 | if (now - lat_info->last_scale_event >= | |
709 | ((u64)NSEC_PER_SEC * 5)) | |
710 | lat_info->scale_grp = NULL; | |
711 | next_lock: | |
712 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
713 | next: | |
714 | blkg_put(blkg); | |
715 | } | |
716 | rcu_read_unlock(); | |
717 | } | |
718 | ||
719 | int blk_iolatency_init(struct request_queue *q) | |
720 | { | |
721 | struct blk_iolatency *blkiolat; | |
722 | struct rq_qos *rqos; | |
723 | int ret; | |
724 | ||
725 | blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL); | |
726 | if (!blkiolat) | |
727 | return -ENOMEM; | |
728 | ||
729 | rqos = &blkiolat->rqos; | |
beab17fc | 730 | rqos->id = RQ_QOS_LATENCY; |
d7067512 JB |
731 | rqos->ops = &blkcg_iolatency_ops; |
732 | rqos->q = q; | |
733 | ||
734 | rq_qos_add(q, rqos); | |
735 | ||
736 | ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); | |
737 | if (ret) { | |
738 | rq_qos_del(q, rqos); | |
739 | kfree(blkiolat); | |
740 | return ret; | |
741 | } | |
742 | ||
743 | timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); | |
744 | ||
745 | return 0; | |
746 | } | |
747 | ||
8c772a9b LB |
748 | /* |
749 | * return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise | |
750 | * return 0. | |
751 | */ | |
752 | static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) | |
d7067512 JB |
753 | { |
754 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
d7067512 JB |
755 | u64 oldval = iolat->min_lat_nsec; |
756 | ||
757 | iolat->min_lat_nsec = val; | |
c480bcf9 DZF |
758 | iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE); |
759 | iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, | |
760 | BLKIOLATENCY_MAX_WIN_SIZE); | |
d7067512 JB |
761 | |
762 | if (!oldval && val) | |
8c772a9b | 763 | return 1; |
5de0073f TH |
764 | if (oldval && !val) { |
765 | blkcg_clear_delay(blkg); | |
8c772a9b | 766 | return -1; |
5de0073f | 767 | } |
8c772a9b | 768 | return 0; |
d7067512 JB |
769 | } |
770 | ||
771 | static void iolatency_clear_scaling(struct blkcg_gq *blkg) | |
772 | { | |
773 | if (blkg->parent) { | |
774 | struct iolatency_grp *iolat = blkg_to_lat(blkg->parent); | |
775 | struct child_latency_info *lat_info; | |
776 | if (!iolat) | |
777 | return; | |
778 | ||
779 | lat_info = &iolat->child_lat; | |
780 | spin_lock(&lat_info->lock); | |
781 | atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE); | |
782 | lat_info->last_scale_event = 0; | |
783 | lat_info->scale_grp = NULL; | |
784 | lat_info->scale_lat = 0; | |
785 | spin_unlock(&lat_info->lock); | |
786 | } | |
787 | } | |
788 | ||
789 | static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, | |
790 | size_t nbytes, loff_t off) | |
791 | { | |
792 | struct blkcg *blkcg = css_to_blkcg(of_css(of)); | |
793 | struct blkcg_gq *blkg; | |
d7067512 JB |
794 | struct blkg_conf_ctx ctx; |
795 | struct iolatency_grp *iolat; | |
796 | char *p, *tok; | |
797 | u64 lat_val = 0; | |
798 | u64 oldval; | |
799 | int ret; | |
8c772a9b | 800 | int enable = 0; |
d7067512 JB |
801 | |
802 | ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); | |
803 | if (ret) | |
804 | return ret; | |
805 | ||
806 | iolat = blkg_to_lat(ctx.blkg); | |
d7067512 JB |
807 | p = ctx.body; |
808 | ||
809 | ret = -EINVAL; | |
810 | while ((tok = strsep(&p, " "))) { | |
811 | char key[16]; | |
812 | char val[21]; /* 18446744073709551616 */ | |
813 | ||
814 | if (sscanf(tok, "%15[^=]=%20s", key, val) != 2) | |
815 | goto out; | |
816 | ||
817 | if (!strcmp(key, "target")) { | |
818 | u64 v; | |
819 | ||
820 | if (!strcmp(val, "max")) | |
821 | lat_val = 0; | |
822 | else if (sscanf(val, "%llu", &v) == 1) | |
823 | lat_val = v * NSEC_PER_USEC; | |
824 | else | |
825 | goto out; | |
826 | } else { | |
827 | goto out; | |
828 | } | |
829 | } | |
830 | ||
831 | /* Walk up the tree to see if our new val is lower than it should be. */ | |
832 | blkg = ctx.blkg; | |
833 | oldval = iolat->min_lat_nsec; | |
834 | ||
8c772a9b LB |
835 | enable = iolatency_set_min_lat_nsec(blkg, lat_val); |
836 | if (enable) { | |
8d75d0ef YK |
837 | if (!blk_get_queue(blkg->q)) { |
838 | ret = -ENODEV; | |
839 | goto out; | |
840 | } | |
841 | ||
8c772a9b LB |
842 | blkg_get(blkg); |
843 | } | |
844 | ||
d7067512 JB |
845 | if (oldval != iolat->min_lat_nsec) { |
846 | iolatency_clear_scaling(blkg); | |
847 | } | |
848 | ||
849 | ret = 0; | |
850 | out: | |
851 | blkg_conf_finish(&ctx); | |
8c772a9b LB |
852 | if (ret == 0 && enable) { |
853 | struct iolatency_grp *tmp = blkg_to_lat(blkg); | |
854 | struct blk_iolatency *blkiolat = tmp->blkiolat; | |
855 | ||
856 | blk_mq_freeze_queue(blkg->q); | |
857 | ||
858 | if (enable == 1) | |
859 | atomic_inc(&blkiolat->enabled); | |
860 | else if (enable == -1) | |
861 | atomic_dec(&blkiolat->enabled); | |
862 | else | |
863 | WARN_ON_ONCE(1); | |
864 | ||
865 | blk_mq_unfreeze_queue(blkg->q); | |
866 | ||
867 | blkg_put(blkg); | |
868 | blk_put_queue(blkg->q); | |
869 | } | |
d7067512 JB |
870 | return ret ?: nbytes; |
871 | } | |
872 | ||
873 | static u64 iolatency_prfill_limit(struct seq_file *sf, | |
874 | struct blkg_policy_data *pd, int off) | |
875 | { | |
876 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
877 | const char *dname = blkg_dev_name(pd->blkg); | |
878 | ||
879 | if (!dname || !iolat->min_lat_nsec) | |
880 | return 0; | |
881 | seq_printf(sf, "%s target=%llu\n", | |
88b7210c | 882 | dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC)); |
d7067512 JB |
883 | return 0; |
884 | } | |
885 | ||
886 | static int iolatency_print_limit(struct seq_file *sf, void *v) | |
887 | { | |
888 | blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), | |
889 | iolatency_prfill_limit, | |
890 | &blkcg_policy_iolatency, seq_cft(sf)->private, false); | |
891 | return 0; | |
892 | } | |
893 | ||
252c651a | 894 | static bool iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s) |
1fa2840e JB |
895 | { |
896 | struct latency_stat stat; | |
897 | int cpu; | |
898 | ||
899 | latency_stat_init(iolat, &stat); | |
900 | preempt_disable(); | |
901 | for_each_online_cpu(cpu) { | |
902 | struct latency_stat *s; | |
903 | s = per_cpu_ptr(iolat->stats, cpu); | |
904 | latency_stat_sum(iolat, &stat, s); | |
905 | } | |
906 | preempt_enable(); | |
907 | ||
908 | if (iolat->rq_depth.max_depth == UINT_MAX) | |
252c651a CH |
909 | seq_printf(s, " missed=%llu total=%llu depth=max", |
910 | (unsigned long long)stat.ps.missed, | |
911 | (unsigned long long)stat.ps.total); | |
912 | else | |
913 | seq_printf(s, " missed=%llu total=%llu depth=%u", | |
914 | (unsigned long long)stat.ps.missed, | |
915 | (unsigned long long)stat.ps.total, | |
916 | iolat->rq_depth.max_depth); | |
917 | return true; | |
1fa2840e JB |
918 | } |
919 | ||
252c651a | 920 | static bool iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s) |
d7067512 JB |
921 | { |
922 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1fa2840e JB |
923 | unsigned long long avg_lat; |
924 | unsigned long long cur_win; | |
925 | ||
07b0fdec | 926 | if (!blkcg_debug_stats) |
252c651a | 927 | return false; |
07b0fdec | 928 | |
1fa2840e | 929 | if (iolat->ssd) |
252c651a | 930 | return iolatency_ssd_stat(iolat, s); |
d7067512 | 931 | |
1fa2840e JB |
932 | avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC); |
933 | cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC); | |
a284390b | 934 | if (iolat->rq_depth.max_depth == UINT_MAX) |
252c651a CH |
935 | seq_printf(s, " depth=max avg_lat=%llu win=%llu", |
936 | avg_lat, cur_win); | |
937 | else | |
938 | seq_printf(s, " depth=%u avg_lat=%llu win=%llu", | |
939 | iolat->rq_depth.max_depth, avg_lat, cur_win); | |
940 | return true; | |
d7067512 JB |
941 | } |
942 | ||
cf09a8ee TH |
943 | static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, |
944 | struct request_queue *q, | |
945 | struct blkcg *blkcg) | |
d7067512 JB |
946 | { |
947 | struct iolatency_grp *iolat; | |
948 | ||
cf09a8ee | 949 | iolat = kzalloc_node(sizeof(*iolat), gfp, q->node); |
d7067512 JB |
950 | if (!iolat) |
951 | return NULL; | |
1fa2840e JB |
952 | iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat), |
953 | __alignof__(struct latency_stat), gfp); | |
d7067512 JB |
954 | if (!iolat->stats) { |
955 | kfree(iolat); | |
956 | return NULL; | |
957 | } | |
958 | return &iolat->pd; | |
959 | } | |
960 | ||
961 | static void iolatency_pd_init(struct blkg_policy_data *pd) | |
962 | { | |
963 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
964 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
965 | struct rq_qos *rqos = blkcg_rq_qos(blkg->q); | |
966 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
967 | u64 now = ktime_to_ns(ktime_get()); | |
968 | int cpu; | |
969 | ||
1fa2840e JB |
970 | if (blk_queue_nonrot(blkg->q)) |
971 | iolat->ssd = true; | |
972 | else | |
973 | iolat->ssd = false; | |
974 | ||
d7067512 | 975 | for_each_possible_cpu(cpu) { |
1fa2840e | 976 | struct latency_stat *stat; |
d7067512 | 977 | stat = per_cpu_ptr(iolat->stats, cpu); |
1fa2840e | 978 | latency_stat_init(iolat, stat); |
d7067512 JB |
979 | } |
980 | ||
451bb7c3 | 981 | latency_stat_init(iolat, &iolat->cur_stat); |
d7067512 JB |
982 | rq_wait_init(&iolat->rq_wait); |
983 | spin_lock_init(&iolat->child_lat.lock); | |
ff4cee08 | 984 | iolat->rq_depth.queue_depth = blkg->q->nr_requests; |
a284390b | 985 | iolat->rq_depth.max_depth = UINT_MAX; |
d7067512 JB |
986 | iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth; |
987 | iolat->blkiolat = blkiolat; | |
988 | iolat->cur_win_nsec = 100 * NSEC_PER_MSEC; | |
989 | atomic64_set(&iolat->window_start, now); | |
990 | ||
991 | /* | |
992 | * We init things in list order, so the pd for the parent may not be | |
993 | * init'ed yet for whatever reason. | |
994 | */ | |
995 | if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) { | |
996 | struct iolatency_grp *parent = blkg_to_lat(blkg->parent); | |
997 | atomic_set(&iolat->scale_cookie, | |
998 | atomic_read(&parent->child_lat.scale_cookie)); | |
999 | } else { | |
1000 | atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE); | |
1001 | } | |
1002 | ||
1003 | atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE); | |
1004 | } | |
1005 | ||
1006 | static void iolatency_pd_offline(struct blkg_policy_data *pd) | |
1007 | { | |
1008 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1009 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
8c772a9b LB |
1010 | struct blk_iolatency *blkiolat = iolat->blkiolat; |
1011 | int ret; | |
d7067512 | 1012 | |
8c772a9b LB |
1013 | ret = iolatency_set_min_lat_nsec(blkg, 0); |
1014 | if (ret == 1) | |
1015 | atomic_inc(&blkiolat->enabled); | |
1016 | if (ret == -1) | |
1017 | atomic_dec(&blkiolat->enabled); | |
d7067512 JB |
1018 | iolatency_clear_scaling(blkg); |
1019 | } | |
1020 | ||
1021 | static void iolatency_pd_free(struct blkg_policy_data *pd) | |
1022 | { | |
1023 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1024 | free_percpu(iolat->stats); | |
1025 | kfree(iolat); | |
1026 | } | |
1027 | ||
1028 | static struct cftype iolatency_files[] = { | |
1029 | { | |
1030 | .name = "latency", | |
1031 | .flags = CFTYPE_NOT_ON_ROOT, | |
1032 | .seq_show = iolatency_print_limit, | |
1033 | .write = iolatency_set_limit, | |
1034 | }, | |
1035 | {} | |
1036 | }; | |
1037 | ||
1038 | static struct blkcg_policy blkcg_policy_iolatency = { | |
1039 | .dfl_cftypes = iolatency_files, | |
1040 | .pd_alloc_fn = iolatency_pd_alloc, | |
1041 | .pd_init_fn = iolatency_pd_init, | |
1042 | .pd_offline_fn = iolatency_pd_offline, | |
1043 | .pd_free_fn = iolatency_pd_free, | |
1044 | .pd_stat_fn = iolatency_pd_stat, | |
1045 | }; | |
1046 | ||
1047 | static int __init iolatency_init(void) | |
1048 | { | |
1049 | return blkcg_policy_register(&blkcg_policy_iolatency); | |
1050 | } | |
1051 | ||
1052 | static void __exit iolatency_exit(void) | |
1053 | { | |
fa1c3eaf | 1054 | blkcg_policy_unregister(&blkcg_policy_iolatency); |
d7067512 JB |
1055 | } |
1056 | ||
1057 | module_init(iolatency_init); | |
1058 | module_exit(iolatency_exit); |